Stage 2: Dose-comparison assessment of rate of flow over the range of 150 to 1,500 units of Hylenex. Each subject will receive a SC infusion of 400 mL (from a 0.5 L bag) of Ringer’s lactate solution in each upper arm. The SC injection sites will be randomized in a double-blinded fashion to either Hylenex or an equal volume of saline solution injected into a Y-port in the tubing just above the catheter immediately prior to infusion. 24-gauge angiocatheters will be placed symmetrically in the SC space in both proximal upper extremities at the lateral aspect, midline halfway between the olecranon process and the inferoposterior aspect of the acromion, introduced at a 30-degree angle. In each arm, Ringer’s lactate solution will be infused SC by gravity (wide open) by placing the top of the fluid in a 0.5 liter bag at a height of 100 cm above the respective catheter sites. Subjects will be dosed in either two or three sequential cohorts.